What does Ackley improved mean?

When you change a regular caliber to be Ackley improved you change the angle of the shoulder and placement of the shoulder. I don't know the exact angles but it does allow you to put a little more powder and in the end increases the bullets velocity. Don't quote me on this but that's what I understand AI to be.
 
When a cartridge is Ackely Improved, most of the taper in the case body is removed and the shoulder is changed from the parent cartridge shoulder angle to 40 degrees. This can be done by simply firing a factory case in an AI rifle chamber.

The resulting AI case actually has ~0.004" less headspace than the parent cartridge (257 AI versus standard 257 Roberts case, for example), so in order to re-chamber a rifle from the parent cartridge to the AI version, the barrel on the rifle needs to be set back at least on thread and an AI reamer used to cut the chamber.

A new unchambered barrel can just be chambered, threaded, and head spaced to fit an action with an AI reamer.

HTH - BCB
 
Ackley was actually the guys last name (P.O. Ackley)that figured out the shoulder angel of a case and that the angel he came up with actually "improved" the ballistics. Here in Utah there are some P.O. Ackley guns that will show up occasionally at gun shows. You better have your check book and credit cards available if you want one of his original builds.
 
Last edited:


Write your reply...
Back
Top